Geographic Range

Anguispira alternata, a land snail commonly called the flamed disc, is native to the Nearctic region. It is found as far north as New Brunswick, Canada, south to northern Florida, and west to northeastern Texas, Kansas and western Minnesota. Additional collections have been recorded further west, in Oregon, Alberta, and central Saskatchewan. ("Anguispira alternata", 2003; Hubricht, 1985)

Habitat

Flamed discs are terrestrial snails found in a variety of habitats. These include forests, weedy roadsides, and along railroads, as well as gardens or vacant lots in urban areas. They are usually found around logs, hollow trees, and rocks in wooded areas. Flamed discs are a temperate climate species, although they can tolerate temperatures as low as -14°C. (Burch and Jung, 1988; Hubricht, 1985; Riddle and Miller, 1988)

Physical Description

Flamed discs are medium-sized snails, typically ranging from 17-25 mm in diameter. Shells average 20 mm wide and 12 mm tall, and so are considered to have a depressed helicoform shape (width greater than height). Shell coloration is pale yellow to brown, with irregular reddish-brown and brown blotches on the upper surface and reddish-brown streaks on the lower surface. These snails' shells have 5 1/2 to 6 whorls, with smooth embryonic whorls, and an umbilicus measuring almost a third of its width. There is a noticeable opening at bottom of the shell (within the whorls). The rest of the shell has ridges which diminish at the base of the shell and it is strongly angular peripherally. The aperature has an thin, unexpanded lip. (Baker, 1939; Burch and Jung, 1988; Pilsbry, 1948)

Development

Generally, land snails deposit their eggs in moist areas, secreting a substance to make egg masses stick to substrate or burying them in shallow holes (1.5 to 2.5 cm in depth). In captivity, eggs have measured 2 to 3 mm in diameter. Time to hatching depends on environmental conditions such as moisture and temperature; typically, land snails hatch within 30 to 45 days. Shells under 5 mm in diameter are much more fragile than larger ones, and because of this, most mortalities occur before snails reach this size. Some studies have indicated that young grow rapidly during their first summer, attaining near-adult sizes by the fall. ("Carnegie Museum of Natural History", 2013; Burch and Pearce, 1990; Douglas, 1963; Elwell and Ulmer, 1971; Tompa, 1984)

Reproduction

Stylommatophoran land snails are hermaphroditic. Although they usually mate with other snails, they may also self-fertilize. Mating partners may be located by following their mucus trails. After a courtship ritual, typically lasting at least a few hours, snails copulate. One snail will mount the shell of the other; each snail inserts spermatophores into the other using a penis. Each will produce fertilized eggs. (Asami, et al., 1998; Burch and Pearce, 1990; Tompa, 1984)

Land snails generally breed during the warmer months of the year, and rain may increase mating. In a laboratory setting, individuals of this species require exposure to low temperatures before they will reproduce, indicating that reproduction is linked to the end of hibernation at the end of colder winter months. Sexual maturity is likely reached when the lip forms on the shell aperture. In cooler or drier areas, growth, and therefore time to sexual maturity, is slower than in warmer, moist areas; populations in Iowa have been noted to reach maturity in their second or third summers of life; in these same populations, sperm were not released by a snail until its shell reached 9 mm in diameter, and snails did not deposit eggs before reaching 13 mm in diameter. In captivity, individuals are noted to lay 2-25 eggs per season, but may lay as many as 40. ("Carnegie Museum of Natural History", 2013; Burch and Pearce, 1990; Douglas, 1963; Elwell and Ulmer, 1971; Perez and Cordiero, 2008; Tompa, 1984)

In Kansas, flamed discs were observed living in groups ranging from 16 to 75 snails per square foot, burrowing together to overwinter; young and juvenile snails are often found in large groups as well. In the fall, these snails reduce their water content (aestivate) and evacuate their guts as a survival aid in cold temperatures, forming an epiphram near the bend of the shell's body whorl. (Douglas, 1963; Elwell and Ulmer, 1971)

The upper tentacles of stylommatophoran species are light and chemosensitive. They may use olfactory gradients in still air to locate food items. Eyes, located at the top of the tentacles, can detect light, as well as general forms at night. The anterior tentacles are chemosensory and the labia detect both touch and chemicals. Repeated experiments with flamed discs found that these snails will change their behavior when a barrier to food is encountered. (Atkinson, 2003; Atkinson, 2013; Nordsieck, 2011; Shearer and Atkinson, 2001)

Predation

Specific predators are not known for this species, but in general, land snails are preyed on by lampyrid beetle larvae or other insects, birds, rodents, and small mammals, particularly chipmunks, voles and shrews. They are also prey to carnivorous land snails. (Burch and Pearce, 1990; Elwell and Ulmer, 1971; Painter, 2013)

Economic Importance for Humans: Positive

While flamed discs do not provide any known benefits specifically, land snails play an important role in breaking down forest detritus, helping to keep these ecosystems healthy and in balance. (Burch and Pearce, 1990)

Economic Importance for Humans: Negative

Although they may serve as intermediate hosts to parasites which later live in small mammals, flamed discs do not pose any significant threats to humans. (MDNR wildlife diseases laboratory, 2013)

Contributors

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

detritivore

an animal that mainly eats decomposed plants and/or animals

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

herbivore

An animal that eats mainly plants or parts of plants.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

mycophage

an animal that mainly eats fungus

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

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The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.